The present invention relates to a silicone lubricant composition and more specifically the present invention relates to a silicone lubricant composition for lubricating hard metal surfaces or soft metal surfaces such as copper or bronze.
Silicone lubricants are well known for hard metal surfaces. Such silicone lubricants usually comprise an organopolysiloxane polymer which may be dimethylpolysiloxane polymer, a methyl, higher-alkyl substituted polysiloxane polymer, or chlorophenyl or tetrachlorophenyl substituted polysiloxane polymer. Also, there are silicone lubricants in which the base lubricating fluid is composed of a trifluoropropyl substituting organopolysiloxane polymer. These fluids may be utilized by themselves or with various other additives for the lubrication of metal surfaces. For instance methyl, higher-alkyl substituted organopolysiloxane polymers are very effective for lubricating hard metal surfaces. In addition dimethylpolysiloxanes with various chlorinated additives are also known for lubricating hard metal surfaces such as for instance disclosed in Agens U.S. Pat. 2,837,482 which disclosure is incorporated in the present case by reference. Such chlorinated additives as described in the foregoing Agens Patent consist of octyltetrachlorobenzoate, dioctyltetrachlorophthalate and bis-2-ethylhexyl tetrachlorophthalate. In addition various types of chlorinated phthalates can be utilized as additives for dimethylpolysiloxanes such as bis-2-alkylhexyltetrachlorophthalates. In these compounds the alkyl may contain anywhere from 2 to 8 carbon atoms. As one example for instance the methyl, higher-alkyl substituted polysiloxanes have been shown to be effective as a lubricant for hard metals or any metal if they have a film thickness three times the surface roughness which for most hard metal surfaces would require film thickness of 30 to 45 micro inches. Most silicone lubricants and specifically methyl, higher-alkyl substituted polysiloxanes have a film thickness from 20 to 30 micro inches. Accordingly, what happens with hard metals is that the methyl higher-alkyl substituted polysiloxanes allow a slow attrition of the asperites in the metal surface and an improvement of the metal surface to a roughness of 5 micro inches which depth of surface roughness can be handled by the methyl higher-alkyl substituted polysiloxanes to lubricate such hard metal surfaces. For dimethylpolysiloxanes which are not as effective as the methyl higher-alkyl substituted polysiloxanes in lubricating metal surfaces, it is necessary to also add a chlorinated additive. Conventional chloride additives may also be added to methyl tetrachlorophenyl substituted polysiloxanes to form ferrous chloride hydrate compounds at the surface of the hard metal which is being lubricated so that the oxy chloride will shear off under stress and prevent undue wear against the hard metal surface. Accordingly in summary, it has been found out that methyl higher-alkyl substituted polysiloxane with or without additives will function in most cases as an effective lubricant for hard metals the dimethylpolysiloxane lubricants will function as lubricants for hard metals with the addition of chloride additives and that tetrachlorophenyl substituted polysiloxanes will function to some extent without additives in lubricating hard metal surfaces but will function most effectively with the use of chlorinated additives in the lubrication of hard metal surfaces. The reason the dimethylpolysiloxane polymers and the tetrachlorophenyl substituted polymers need the additives, is that they do not form as an effective thickness of film on the hard metal surfaces as is possible with the methyl higher-alkyl substituted polysiloxanes. However, all of these organopolysiloxane lubricants as well as others that haven't been mentioned above with or without the traditional chlorinated additives have a serious deficiency when it comes to lubricating soft metals, such as brass, bronze, soft steel, free machining steel, lead, copper, etc. In the case where the organopolysiloxane polymers are applied to lubricate soft metals, the wear rate is initially low and a low sliding friction prevails then after a short period of low wear a very high rate wear is experienced with a sizable increase in the sliding friction causing the metal parts to wear away at a higher rate.
It should also be pointed out that such chlorinated additives such as those of the Agens Patent are not as effective as would be desired even with silicone polymers in lubricating soft metals. When silicone lubricants are applied to lubricate soft metal, even in the case with methyl higher-alkyl substituted polysiloxanes that such prior chlorinated additives have to be utilized at very high concentrations of 4 to 10% by weight of the lubricating composition to effect any sizable change in the performance of the lubricant composition. Accordingly, it was highly desirable to be able to formulate an additive which could be utilized at small concentrations for addition to silicone polymers to prepare silicone lubricant compositions for the lubrication of soft metals. If was desired that such silicone lubricant with the additive in it would form oxychloride compounds on the soft metal surface and the soft metal being in contact with another soft metal or even a hard metal would allow the oxychloride compounds to shear off thus protecting the soft metal surface from wear. Prior art chloride additives needed to be utilized at high concentration as additives to silicone lubricants, since they were not very efficient in forming oxy chloride compounds at the point of wear.
Accordingly, it was thought it would be highly advantageous to obtain some type of chlorinated additive for such silicone lubricant which would form the appropriate type of oxychloride compounds which were needed for soft metal surfaces such as copper and bronze. Then the oxychloride compounds would be sheared off instead of the soft metal and allow the soft metal to wear gradually and not at a high rate as was experienced previously. Accordingly, it was highly desirable to formulate and obtain an additive for silicone polymers utilized in forming lubricant compositions which such additive would decrease the wear of hard metal surfaces but would more importantly decrease the wear of soft metal surfaces when they acted upon each other or when a soft metal surface acted against a hard metal surface. It should be noted that the foregoing discussion above as to the formation of oxychloride compounds at the surfaces of the metals and the function of such compounds preventing undue waer is a theoretical discussion.
In summary, what was needed was chlorinated additive or other type of additive for polysiloxane polymers that could be utilized as a lubricant to decrease the wear of metal surfaces acting against each other, which was much more efficient than the prior art organopolysiloxane polymers with various additives such as those for instance disclosed in the foregoing Agens U.S. Pat. No. 2,837,482.
Accordingly, it is one object of the present invention to provide for an additive for silicone lubricants which would decrease the wear of hard metal surfaces lubricated by such silicone polymers.
It is another object of the present invention to provide an additive for a silicone lubricating composition which would decrease the wear when such silicone lubricants was utilized to lubricate soft metal surfaces.
There is an additional object of the present invention to provide for an additive for a silicone lubricant composition which would decrease the wear when such lubricant composition was utilized to lubricate soft or hard metal surfaces acting against each other.
It is yet an additional object of the present invention to provide for a silicone lubricant composition which has excellent lubricity properties for lubricating copper, bronze, and brass surfaces. These and other objects of the instant invention are accomplished by the means of the disclosure set forth herein below.